GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2002 🢒 Cavalier (CNG) 🢒 Engine 🢒 Engine Controls - 2.2L (LN2) 🢒 Fuel Indicator Lamp Always On - Alternative Fuels

Circuit Description

The fuel gage select switch assembly contains 2 components. The fuel gage select switch is used to indicate to the Alternative Fuels Engine Control Module (AF ECM) that the operator of the vehicle has requested the fuel gage display the level of fuel for the DORMANT or non-operating fuel system. The fuel indicator lamp (FIL) is used by the AF ECM to indicate to the operator of the vehicle which fuel system is in use. When illuminated the vehicle is operating on gasoline.

The fuel indicator lamp (FIL) is supplied power by the ignition relay and the ground path is supplied by the AF ECM. The AF ECM will supply ground to the FIL for a two second bulb check at ignition ON during CNG operation or continuously during gasoline operation when the ignition is in the ON or RUN positions.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. The System Check MUST be performed before proceeding with this diagnostic table. Failure to perform the System Check will result in mis-diagnosis.

    2.

  2. This step checks for proper operation of the FIL.

    3.

  3. The FIL should only stay illuminated when the engine is operating on gasoline.

    4.

  4. The Alternative Fuels Operation (AFO) Enable Input and AFO Enable Output parameters both indicate the state of the AFO Enable circuit. The Input parameter is the state of the enable circuit as monitored by the gasoline control module. The Output parameter is the state of the enable circuit as commanded by the AF ECM.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perfrom the Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Alternative Fuels (Engine Controls)

2

  1. Turn the ignition OFF and wait 30 seconds.
  2. Observe the fuel indicator lamp (FIL) located in the fuel gage select switch button.
  3. Turn the ignition ON leaving the engine OFF.

Did the FIL illuminate for at least a 2 second bulb check?

Go to Step 3

Go to Fuel Indicator Lamp Inoperative - Alternative Fuels

3

  1. Start and idle the engine.
  2. Observe the fuel indicator lamp.

Is the fuel indicator lamp ON while the engine is running?

Go to Step 4

System OK

4

  1. Using the scan tool establish communications with the AF ECM.
  2. Observe the Alternative Fuels Operation (AFO) enable parameters and determine if the engine is operating on GASOLINE.

Is the engine operating on GASOLINE?

Go to Step 5

Go to Step 6

5
  1. Determine the cause of gasoline engine operation. Possible causes include the following:
    2. • Empty CNG fuel tank
    • An inaccurate fuel tank pressure (FTP) sensor indicates no CNG fuel when tank has fuel
    • An AF ECM DTC is set
  2. Fill CNG tank or repair vehicle as necessary.

Was one of the listed causes found and repaired?

Go to Step 10

Go to Fuel System Unwanted Switch to Gasoline in Engine Controls

6
  1. Remove the fuel gage select switch from the instrument panel. Refer to Alternative Fuel Gage Selector Switch/Fuel Indicator Lamp Replacement .
  2. Disconnect the fuel gage select switch connector.
  3. Connect the J 35616-200 Unpowered Test Lamp between the Fuel Indicator Control circuit terminal and the bulb power circuit terminal.
  4. Observe the test lamp as you start and idle the engine.

Is the test lamp illuminated while the engine is running?

Go to Step 7

Go to Step 8

7
  1. Turn the ignition OFF and wait 30 seconds.
  2. Disconnect the AF ECM connectors.
  3. Test the Fuel Indicator Control circuit for a short to ground.
  4. Repair wiring as necessary.

Was a wiring repair necessary?

Go to Step 10

Go to Step 9

8

Replace the fuel gage select switch assembly. Refer to Alternative Fuel Gage Selector Switch/Fuel Indicator Lamp Replacement .

Is the replacement complete?

Go to Step 10

--

9
  1. Replace the AF ECM. Refer to Alternative Fuels Engine Control Module Replacement .
  2. Program-flash- the replacement control module with the correct vehicle software and calibration.

Is the replacement complete?

Go to Step 10

--

10
  1. Remove all test equipment except the scan tool.
  2. Connect any disconnected components, fuses, etc.
  3. Using a scan tool clear DTC Information from the AF ECM and the gasoline control module (VCM/PCM or ECM).
  4. Turn the ignition OFF and wait 30 seconds.
  5. Start the engine and operate the vehicle.
  6. Observe the fuel indicator lamp and the MIL.
  7. Observe vehicle performance and driveability.
  8. After operating the vehicle inspect BOTH control modules for stored DTCs.

Does the vehicle operate on CNG with normal driveability, no FIL/MIL illumination and no stored DTCs?

System OK

Go to Diagnostic System Check - Alternative Fuels (Engine Controls)